The Prime Minister is appointed by a vote in the Thai House of
Representatives by a simple majority, he is then officially
sworn-in and endorsed by the King of Thailand.
His selection is usually based on the fact that he is either the
leader of the largest political party in the lower house or the
leader of the largest coalition of parties. In accordance with the
constitution the Prime Minister can only be appointed twice and is
therefore limited to a maximum of two consecutive terms. The
current incumbent is Abhisit Vejjajiva, leader of the Democrat Party, since 17
December 2008.[1]

Prior to 1932 Thailand was ruled by absolute monarchs,
who acted as both the head of state and the government. However
during the middle and latter reigns of the Chakri Dynasty
several individuals were perceived to hold a post equivalent to a
head of government. During the reign of King Mongkut: Somdet Chao PhrayaSi
Suriyawongse, had a very significant role in an otherwise
absolutist system. During the reign of King Chulalongkorn, Prince Damrong
Rajanubhab took over this role. In fact the office most
considered the precursor of that of the Prime Minister was the
ancient office of Samuha Na Yok (สมุหนายก), which was ran
by an Akra Maha Senabodi (อัครมหาเสนาบดี) or Chief
Minister in charge of civilian affairs.

The first Prime Minister of Siam was Phraya Manopakorn Nititada a
civil servant and lawyer. The title of the office changed from
"Prime Minister of Siam" to "Prime Minister of
Thailand" in 1945 and then permanently with the renaming of
Siam to Thailand in 1949. For most of its existence the office has
been occupied by Army leaders; fifteen out of
twenty-seven. Beginning with the country's second Prime Minister:
Phot
Phahonyothin, who ousted his predecessor in a coup in 1933. The longest
serving Prime Minister was Field MarshalPlaek
Pibulsonggram at 14 years, 11 months and 18 days. The shortest
was Tawee
Boonyaket at only just 18 days.[2] Nine
were removed by coups d'état, two were disqualified by
court order, and eleven resigned from office. The youngest ever to
occupy office was M.R. Seni Pramoj at 40 years old. Every Prime
Minister since Phraya Manopakorn Nititada has been Buddhist.

Appointment

The Prime Minister of the Kingdom of Thailand
must be a member of the House of
Representatives of Thailand[3].
Therefore the qualifications for the office is the same as the
qualifications for the House.

To be appointed the nominee for the office must have the support
of one-fifth of the members of the House of Representatives. Then
after a simple-majority vote in the House, a resolution will be
passed and submitted to the King of Thailand,
who will then make a formal appointment by giving his royal assent
to the resolution. This must be done within thirty days of the
beginning of the first session of the House of Representatives
after an election. If no candidate can be found within this time
then it is the duty of the President of
the National Assembly of Thailand to submit the name he
considers most worthy for the King to formalize.

The nominee and eventual Prime Minister is always the leader of
the largest political party
in the lower house or the leader of the majority coalition formed
after an election.

Function

The Prime Minister is the de facto chairman of the Cabinet of
Thailand. The appointment and removal of Ministers can only be made with
his advice. As the leader of the government the Prime Minister is
therefore ultimately responsible for the failings and performance
of his Ministers and the government as a whole. The Prime Minister
cannot hold office for a consecutive period of more than eight
years. As the most visible member of the government the Prime
Minister represent the country abroad as well as the main
spokesperson for the government at home. The Prime Minister must,
under the constitution, lead the Cabinet in announcing the
government's policy statement in front of a joint-session of the
National Assembly, within fifteen days of being sworn-in.[4]

The Prime Minister is also directly responsible for many
departments, these include: the National Intelligence Agency, the
Bureau of the Budget, the Office of the National Security Council,
the Office of the Council of State, the Office of the Civil Service
Commission, the Office of the National Economic and Social
Development Board, the Office of Public Sector Development
Commission and the Internal Security
Operations Command. Legislatively all money bills introduced in
the National Assembly must require the Prime Minister's
approval.

The Prime Minister can be removed by a vote of no confidence. This process can be
evoked, firstly with the vote of only one-fifth of the members of
the House of Representatives for a debate on the matter. Then after the debate a
vote will be taken and with a simple majority the Prime Minister
can be removed. This process cannot be repeated within one
parliamentary session.

The official residence of the Prime
Minister is Baan Phitsanulok (บ้านพิษณุโลก) or Phitsanulok House, also at
the center of Bangkok. The
house was build during the reign of King Vajiravudh, it
became an official place of residence in 1979. The House is however
rumored to have many ghosts, therefore most Prime Ministers live at
their own private residences and only use the house for official
business.

Deputy
Prime Minister

Several Deputy Prime Ministers of Thailand
(รองนายกรัฐมนตรี) can be
appointed. This position can be combined with other ministerial
portfolios.